A person B is located 350 meters east from a person A. Person A starts riding a bike north at a rate of 5 m/sec and 7 minutes later person B starts riding a bike south at a rate 3 m/sec. At what rate is the distance separating the two people changing 25 minutes after person A starts riding?
So i guess my biggest problem is that I'm having a hard time understanding this question…
so I am given dx/dt = 3m/sec
and I have to find dy/dt when x=25?? Can someone provide a basic guideline on how to approach this question?
Best Answer
Start by defining your axes and variables. Let East be $+x$, North be $+y$, measured in meters with time in seconds. If A starts at the origin, B starts at $(350,0)$ As A is riding North, his location at time $t$ is $(0,5t)$ What is B's location after he starts riding? Now find the distance $d$ as a function of time. You are then asked for $\frac {dd}{dt}$ at 25 minutes.